This invention relates to rough terrain vehicles, and more particularly, to a frame for a rough terrain vehicle which supports and maintains the vehicle platform and body in a relatively level position even when the vehicle is traveling along a slanted grade or uneven terrain.
Many vehicles have been designed to operate off of improved roadways or highways and over uneven or rough terrain. Examples of such off-the-road or all-terrain vehicles can be found in my co-invented prior U.S. Pat. Nos. 3,917,306, 3,506,079 and 3,525,534. This invention is an improvement over the prior constructions and is particularly directed to a vehicle for traveling along slanted grades such as commonly found in drainage culverts along highways or the like. Such vehicles are commonly used to mow the grass along roadways. Other applications of the rough terrain vehicle of this invention may include fork lifts or ditching machines which have elongate digging blades entrenched on the ground that are prone to break if the ditching machine is unlevel. It will also be understood that this invention is applicable to any type of vehicle for traversing rough, uneven or slanted terrain.
Vehicles for traveling in drainage culverts and the like typically take the form of conventional tractors which have a rigid one-piece frame and a fixed wheelbase. When such a vehicle travels along a slanted grade, the wheels on one side of the vehicle are lower than the wheels on the other side of the vehicle, and the vehicle body necessarily adopts a tilted orientation roughly equal to the slanted grade of the ground. The tilted orientation of the vehicle body can be quite uncomfortable for the driver, particularly when the grade is steep. Irregularities or bumps on the slanted grade can also cause one or more of the wheels to lift off the ground, which impacts the driver's ability to control the vehicle. There is also always the danger of the vehicle rolling over.
In addition, the slanted orientation of the vehicle transmits torsional stresses to the frame which causes strain and damage to the vehicle body. The tilted orientation of the vehicle body also shifts the center of gravity of the vehicle over the wheels and reduces the amount of traction between one or more of the wheels and the ground. When one of the wheels encounters a bump on the ground surface, additional torsional forces are applied to the frame which can further tilt and cause vibration in the vehicle frame. Obviously, the accumulation of the slanted orientation of the vehicle body, the loss of traction of the wheels, and the torsional stresses and vibrations produced in the vehicle body provide less than a comfortable ride which often causes the driver physical fatigue.
An important aspect of this invention therefore lies in providing a vehicle frame for a rough terrain vehicle which maintains the vehicle platform and body at a relatively level orientation even when the vehicle is traveling along a slanted grade or uneven terrain. Such results are achieved by providing a vehicle frame which includes four independently movable frame arms which each have a wheel mounted thereon. Pivot means connect the frame arms at approximately the midpoint of the vehicle and permit relative independent movement of each of the frame arms about the pivot means. Connecting means and control means are associated with the frame arms on each side of the vehicle for controlling relative movement of the frame arms.
When the wheels on one side of the vehicle fall out of level with the wheels on the other side of the vehicle, the connecting and control means are operable to adjust the relative positions of the frame arms on each side of the vehicle so that a central axle at a midpoint of the vehicle remains relatively level. The vehicle platform and body are supported on the central axle so that the vehicle platform and body also remain relatively level even when the vehicle travels along a slanted grade. The connecting and control means are also operable to maintain the vehicle body in a relatively level position when only one of the wheels encounters a bump or irregularity on the ground surface.
Other features, advantages, and objects of the invention will become apparent from the specification and drawings.